📚 Case Study Practice in Year 7 CCEA Science | CCEA 七年级科学案例分析实战
This article takes you through a series of practical case studies that mirror the style of CCEA Year 7 Science assessments. Each case presents a real-world investigation with data, observations and questions. You will learn how to identify variables, present results, draw evidence-based conclusions and evaluate experimental methods. Working through these examples step by step will build your confidence and scientific thinking skills.
本文将带您完成一系列实践案例研究，这些案例模拟了 CCEA 七年级科学评估的风格。每个案例都呈现了一项真实世界的调查，包含数据、观察和问题。您将学习如何识别变量、展示结果、得出基于证据的结论，并评估实验方法。逐步完成这些示例将增强您的信心和科学思维能力。
1. Understanding a Scientific Case Study | 理解科学案例分析
A case study in science is a detailed account of an investigation. It usually includes a hypothesis, a method, a set of results and sometimes a conclusion or evaluation. CCEA exam questions often present a scenario and ask you to apply your scientific knowledge and enquiry skills. You need to read carefully, pick out key information and think like a scientist.
科学中的案例分析是对一项调查的详细描述。它通常包括假设、方法、一系列结果，有时还包括结论或评价。CCEA 考试题常会呈现一个情景，要求你运用科学知识和探究技能。你需要仔细阅读，提取关键信息，并像科学家一样思考。
In Year 7, you will encounter case studies linked to biology, chemistry and physics topics such as plant growth, dissolving, shadows and ecosystems. The core skills remain the same: identify what was changed, what was measured and what was kept the same. Then you analyse the data, spot patterns and suggest improvements.
在七年级，你会遇到与生物学、化学和物理学主题相关的案例研究，例如植物生长、溶解、影子和生态系统。核心技能是相同的：确定改变了什么、测量了什么、保持了哪些不变。然后分析数据，发现规律，并提出改进建议。
2. Case Study 1: The Bean Plant Growth | 案例一：豆苗的生长
A student wanted to find out how the amount of water affects the growth of bean plants. She planted seeds in three identical pots of soil and placed them on the same sunny windowsill. Pot A received 20 ml of water each day, Pot B received 40 ml, and Pot C received 60 ml. After 10 days, she measured the height of the plants.
一位学生想了解水量如何影响豆苗的生长。她把种子种在三个相同的装有土壤的盆中，并把它们放在同一个阳光充足的窗台上。A 盆每天浇水 20 ml，B 盆每天 40 ml，C 盆每天 60 ml。10 天后，她测量了植株的高度。
| Pot / 盆 | Water per day / 每日水量 | Height after 10 days / 10天后高度 |
|---|---|---|
| A | 20 ml | 5 cm |
| B | 40 ml | 8 cm |
| C | 60 ml | 7 cm |
The independent variable in this experiment is the amount of water given each day. The dependent variable is the height of the bean plants after 10 days. Controlled variables include the type of soil, the size of the pots, the amount of sunlight and the type of seed. These must stay the same to make the test fair.
这个实验中的自变量是每天浇灌的水量。因变量是 10 天后豆苗的高度。控制变量包括土壤类型、盆的大小、光照量和种子类型。这些必须保持不变，以保证测试的公平性。
The results show that 40 ml per day produced the tallest plant (8 cm), while 20 ml resulted in a smaller plant (5 cm). Surprisingly, the plant receiving 60 ml was shorter than the 40 ml plant. This may be because too much water made the soil waterlogged, reducing the oxygen available to the roots. The conclusion is that there is an optimum amount of water for growth; too little stunts growth and too much can be harmful.
结果显示，每天 40 ml 的浇水量长出了最高的植株（8 cm），而 20 ml 的植株较矮（5 cm）。令人惊讶的是，浇 60 ml 的植株比 40 ml 的更矮。这可能是因为水太多导致土壤积水，减少了根部可获得的氧气。结论是，存在一个最适宜生长的水量；过少会阻碍生长，过多则可能有害。
3. Case Study 2: Dissolving Sugar in Water | 案例二：糖在水中的溶解
A class investigated how temperature affects the time taken for a sugar cube to dissolve. They used a beaker with 200 ml of water, placed it in a water bath at different temperatures, added one sugar cube and stirred gently. They recorded the time until no solid sugar was visible.
一个班级探究了温度如何影响方糖溶解所需的时间。他们使用一个盛有 200 ml 水的烧杯，将其置于不同温度的水浴中，加入一块方糖并轻轻搅拌。他们记录直到看不见固体糖时所用时间。
| Temperature / 温度 (°C) | Dissolving time / 溶解时间 (s) |
|---|---|
| 10 | 120 |
| 20 | 80 |
| 40 | 35 |
| 60 | 15 |
Here the independent variable is the temperature of the water. The dependent variable is the dissolving time. Control variables include the volume of water, the size of the sugar cube, the stirring method and the beaker used. The data show a clear pattern: as temperature increases, the dissolving time decreases.
这里的自变量是水的温度。因变量是溶解时间。控制变量包括水的体积、方糖的大小、搅拌方法和所用的烧杯。数据显示出明确的规律：温度升高，溶解时间缩短。
Using particle theory, we can explain this trend. In warmer water, the water particles move faster and collide with the sugar surface more often and with more energy. This pulls sugar particles into the liquid more quickly. The investigation supports the prediction that higher temperatures speed up dissolving.
我们可以用粒子理论解释这一趋势。在较热的水中，水粒子运动更快，更频繁地撞击糖的表面，且能量更高。这使得糖粒子更快地进入液体中。这项调查支持了温度升高会加速溶解的预测。
4. Case Study 3: Investigating Shadows | 案例三：探究影子
A student placed a torch 50 cm away from a wall and held a wooden block halfway between them. She measured the length of the shadow on the wall. She repeated this with the torch at different distances from the wall. The block always stayed in the middle.
一位学生将手电筒放在距离墙壁 50 cm 处，并在两者中间放一个木块。她测量了墙壁上影子的长度。她分别在不同的手电筒到墙壁距离下重复了这一过程。木块始终放在中间。
| Distance from torch to wall / 手电到墙距离 (cm) | Shadow length / 影子长度 (cm) |
|---|---|
| 20 | 18 |
| 30 | 12 |
| 40 | 8 |
| 50 | 6 |
The independent variable is the distance from the torch to the wall. The dependent variable is the shadow length. The student kept the block size and its position relative to the torch constant. As the distance increased, the shadow became shorter.
自变量是手电筒到墙的距离。因变量是影子的长度。学生保持木块的大小及其相对于手电的位置不变。随着距离增加，影子变短。
This happens because light travels in straight lines. When the torch is closer to the block, the rays spread out and create a larger shadow. When the torch is farther away, the rays reaching the block are more nearly parallel, so the shadow is closer to the actual size of the block. This relationship can be used to create clear shadow images in shadow puppetry.
这是因为光沿直线传播。当手电靠近木块时，光线发散并在墙上产生较大的影子。当手电远离时，到达木块的光线更接近平行，因此影子更接近木块的实际大小。这种关系可用于在皮影戏中创造清晰的影像。
5. Case Study 4: A Pond Food Chain | 案例四：池塘食物链
Below is a simple food chain in a pond ecosystem:
下面是一个池塘生态系统中的简单食物链：
Algae → Water fleas → Small fish → Large fish
藻类 → 水蚤 → 小鱼 → 大鱼
Each arrow represents the flow of energy from one organism to the next. Algae are producers; they make their own food using sunlight. Water fleas are primary consumers, and the fish are secondary and tertiary consumers. Predators depend on prey for food, so changes in one population affect the others.
每个箭头表示能量从一个生物体传递到下一个。藻类是生产者；它们利用阳光自己制造食物。水蚤是初级消费者，鱼类是次级和三级消费者。捕食者依赖猎物作为食物，因此一个种群的变化会影响其他种群。
Imagine a disease kills most of the water fleas. Small fish would have less food, so their numbers would decrease. With fewer small fish, large fish would then also decline. Alternatively, if the water fleas decrease, algae might increase because fewer algae are being eaten. This illustrates the interdependence of organisms in a food chain.
设想一种疾病杀死了大部分水蚤。小鱼的食物减少，它们的数量就会下降。小鱼减少后，大鱼的数量也会下降。或者，如果水蚤减少，藻类可能会增加，因为被捕食的藻类减少了。这说明了食物链中生物的相互依存关系。
Ecologists study such links to understand how pollution or habitat loss can impact the whole ecosystem. In an exam case study, you might be asked to predict what happens if a pollutant kills the algae. Without producers, the entire chain would collapse because no energy enters the system.
生态学家研究这些关联，以了解污染或栖息地丧失如何影响整个生态系统。在考试案例分析中，你可能会被问到如果一种污染物杀死了藻类会发生什么。没有生产者，整个食物链将崩溃，因为没有能量进入系统。
6. Case Study 5: Fair Testing and Variables | 案例五：公平测试与变量
Consider a student who wants to find out whether exercise increases heart rate. She measures her pulse before any exercise (resting), after walking for 2 minutes and after running for 2 minutes. She records the data below.
设想一位学生想知道运动是否会加快心率。她测量了运动前（休息时）、慢走 2 分钟后和快跑 2 分钟后的脉搏。她记录数据如下。
| Activity / 活动 | Heart rate / 心率 (beats/min) |
|---|---|
| Resting / 休息 | 72 |
| Walking / 慢走 | 98 |
| Running / 快跑 | 135 |
In this investigation, the independent variable is the type of activity. The dependent variable is the heart rate. Control variables include the time spent on each activity, the same person doing the test, and taking the measurement in the same way. Without keeping these constant, you could not be sure the heart rate changes were due to the exercise alone.
在这个探究中，自变量是活动类型。因变量是心率。控制变量包括每项活动所用时间、同一个人参与测试，以及用相同方法测量。如果不保持这些不变，就无法确保心率的变化仅由运动引起。
Fair testing is a cornerstone of scientific experiments. Always ask: ‘What have I changed? What am I measuring? What must I keep the same?’ In CCEA case studies, you are often asked to write down one controlled variable. Pick something that really could affect the results if not controlled.
公平测试是科学实验的基石。始终要问：“我改变了什么？我在测量什么？我必须保持什么不变？”在 CCEA 的案例分析中，你经常被要求写出一个控制变量。选择一个如果不控制就会真正影响结果的因素。
7. Case Study 6: Presenting Data | 案例六：展示数据
Look back at the bean plant data in Case Study 1. The three pots are separate categories rather than a continuous range. For categorical variables, a bar chart is the best choice. On a bar chart, the x-axis shows the categories (Pot A, Pot B, Pot C) and the y-axis shows the height in cm. Bars should be of equal width and clearly labelled.
回顾案例一中豆苗的数据。三个盆代表分开的类别，而不是连续的范围。对于分类变量，条形图是最佳选择。在条形图中，x 轴显示类别（A 盆、B 盆、C 盆），y 轴显示高度（厘米）。条形宽度应相等，并清晰标记。
For the dissolving sugar investigation, the temperature is a continuous variable and the dissolving time is also continuous. A line graph is appropriate here. Plot temperature on the x-axis and time on the y-axis. Draw a smooth curve or line of best fit to show the trend. Your graph must include a title, labelled axes with units and an even scale.
对于糖的溶解探究，温度是连续变量，溶解时间也是连续的。这里适合用线图。将温度绘制在 x 轴上，时间绘制在 y 轴上。画一条平滑的曲线或最佳拟合线来展示趋势。你的图表必须包含标题、带单位的轴标签和均匀的刻度。
Always choose the type of chart that makes the pattern most obvious. Bar charts compare discrete groups; line graphs show how one variable changes continuously with another. In a case study, you might be asked to plot data from a table or describe what a graph shows.
始终选择最能清晰展示规律的图表类型。条形图比较离散的组别；线图显示一个变量如何随另一个变量连续变化。在案例分析中，你可能会被要求根据表格数据绘图，或描述图表所显示的内容。
8. Case Study 7: Drawing Conclusions | 案例七：得出结论
A good conclusion states what you found out and supports it with data. For example, from the dissolving sugar case we can say: ‘The investigation shows that as water temperature increases, the time taken for the sugar cube to dissolve decreases. At 10 °C it took 120 seconds, but at 60 °C it only took 15 seconds.’ Then link this to science: ‘This happens because particles move faster in hot water and collide with the sugar more often.’
一个好的结论要说明你发现了什么，并用数据支持。例如，根据糖的溶解案例我们可以说：“研究显示，随着水温升高，方糖溶解所需的时间缩短。在 10 °C 时用了 120 秒，而在 60 °C 时仅用 15 秒。”然后联系科学知识解释：“这是因为热水中粒子运动更快，更频繁地与糖碰撞。”
Avoid jumping to conclusions that are not backed up by evidence. Do not say ‘temperature affects dissolving’ if you only tested four temperatures; say ‘within the range tested, higher temperature led to faster dissolving’. Also, compare your result to the original hypothesis where possible. If the plant with the most water did not grow the tallest, you must explain why the evidence does not match your prediction.
避免得出没有证据支持的结论。如果你只测试了四种温度，不要说“温度影响溶解”，而要说“在测试范围内，温度越高，溶解越快”。此外，尽可能将结果与原始假设进行比较。如果浇水最多的植株没有长得最高，你必须解释为什么证据与你的预测不符。
In an exam, read the data carefully. Describe the trend in words and quote the numbers that prove it. This shows you can handle data and use scientific reasoning simultaneously.
在考试中，仔细阅读数据。用文字描述趋势，并引用证明它的数字。这表明你能够同时处理数据并运用科学推理。
9. Case Study 8: Evaluating the Experiment | 案例八：评价实验
No experiment is perfect. When evaluating a case study, think about possible errors and suggest realistic improvements. For the bean plant experiment, the student might have measured the plants using a ruler that was not lined up properly with the base of the stem. She could have read the measurement at an angle, causing parallax error.
没有完美的实验。在评价一个案例研究时，考虑可能的错误并提出切实可行的改进措施。对于豆苗实验，学生可能没有将尺子对准茎的基部来测量植物。她可能斜着读数，导致视差错误。
To improve reliability, she could repeat the investigation with three pots for each condition and calculate an average. This reduces the effect of a single odd result. Also, she could use a digital calliper instead of a ruler for more precise height measurement. She should make sure the soil type and the amount of light are truly identical by using soil from the same bag and a light meter.
为了提高可靠性，她可以对每种条件重复使用三个盆，然后计算平均值。这可以减少单个异常结果的影响。此外，她可以使用数字卡尺代替直尺，以获得更精确的高度测量。她应通过使用同一袋土壤和照度计，确保土壤类型和光照量确实一致。
Evaluation also involves considering whether the data support the conclusion fully. In the shadow investigation, only four distances were tested. The student could test more distances and repeat each one three times to check for consistency. Mentioning specific improvements shows the examiner you understand how to design a better experiment.
评价还包括考虑数据是否完全支持结论。在影子调查中，只测试了四个距离。学生可以测试更多距离，并对每个距离重复三次以检验一致性。提出具体的改进措施向考官展示你懂得如何设计更好的实验。
10. Exam-Style Case Study Practice | 考试风格的案例分析练习
Read the following scenario: A student wonders whether the size of a beaker affects how long a candle burns. He places identical small candles inside three different beakers: 250 ml, 500 ml and 1000 ml. He lights the candles at the same time, covers each with the beaker, and measures the time until the flame goes out.
阅读以下情景描述：一位学生想知道烧杯的大小是否会影响蜡烛燃烧的时间。他把相同的小蜡烛分别放在三个不同的烧杯内：250 ml、500 ml 和 1000 ml。他同时点燃蜡烛，用烧杯盖住，并测量火焰熄灭的时间。
| Beaker size / 烧杯大小 (ml) | Burning time / 燃烧时间 (s) |
|---|---|
| 250 | 12 |
| 500 | 25 |
| 1000 | 48 |
Identify the independent variable, dependent variable and one control variable. Write a conclusion using data. Evaluate the method and suggest an improvement.
识别自变量、因变量和一个控制变量。用数据写出结论。评价该方法并提出一项改进建议。
Model answer: The independent variable is the beaker size. The dependent variable is the time the candle burns. One control variable is the size of the candle, because using different-sized candles would change the results. The data show that the 1000 ml beaker allowed the candle to burn for 48 seconds, while the 250 ml beaker only 12 seconds. This suggests that there is more oxygen in a larger beaker, so the candle takes longer to use it up. To improve the experiment, the student should repeat each test three times and calculate an average. He could also use a stopwatch more accurate to 0.1 s instead of a clock that only shows whole seconds.
答案示例：自变量是烧杯大小。因变量是蜡烛燃烧的时间。一个控制变量是蜡烛的大小，因为使用不同大小的蜡烛会改变结果。数据显示 1000 ml 的烧杯让蜡烛燃烧了 48 秒，而 250 ml 的烧杯只有 12 秒。这表明更大的烧杯含有更多的氧气，所以蜡烛需要更长时间才耗尽氧气。为了改进实验，学生每种条件应重复测试三次并计算平均值。他还可以使用精确到 0.1 秒的秒表，而不是只能显示整秒的时钟。
11. Key Takeaways and Tips | 关键要点与技巧
When tackling a CCEA case study in your test, always begin by highlighting the question and the data provided. Spend a minute planning: What is the experiment about? What are the variables? Draw simple arrows or notes next to the table to remind you. Make sure you use full sentences in your answers and always include units with numerical values.
Published by TutorHao | Year 7 Science Revision Series | aleveler.com
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